One question astronomers are asked all the time is how our science contributes to the well-being of humankind. This is a fair question -- after all, if we are using your tax dollars, you have a right to ask for some return. Astronomers (myself included) love to wax poetic about the pushing back of the boundaries of the unknown, of discovering our place in the Universe, and other such big ideas. Yes, these are true, but often people really want to know, "What have you done for me lately?"
There are many concrete examples of space science and technology being used in everyday life. One of the next benefits of astronomy you will begin to see in the coming years will be at your eye doctor's office, where the laser technology developed to help astronomers see more clearly into the heavens by removing the distortions of the atmosphere is being adapted to allow opticians, optometrists and ophthalmologists peer clearly into your eye. This will allow for amazingly precise eyeglasses and contact lens prescriptions and allows the doctors to detect eye diseases and problems earlier than before.
An even greater impact is being wielded by satellites that look not out into deep space, but back at the Earth. These satellites allow us to study the Earth in many ways, from the impacts of deforestation across the globe to precise measurements of ocean water heights and temperatures to constant surveillance of the weather. The technologies that permit these vital observations are developed in tandem with technologies needed to make precise astronomical observations.
Right now, Hurricane Dean is crossing the Caribbean Sea and threatening the Yucatan Peninsula and northern Mexico. Because of the multitude of weather satellites, meteorologists knew that Dean was a serious threat to be a monster hurricane threatening these areas days ago, when Dean was a minor hurricane just entering the Caribbean Sea from the Atlantic. Saturday night, when I was flying back to Austin from my visit to Tucson, Arizona, my flight from Dallas to Austin was delayed quite a bit. Our plane was coming into Dallas from Cancun, and the delay was due in large part to many tourists cutting vacations short and trying to fly out of harm's way. While Dean is causing major travel headaches because of this, the extra few days of warning we have had thanks to the bevy of satellites watching the storm and the general weather in the region has allowed thousands of people to move to safety.
These same warnings were available for New Orleans many days prior to the arrival of Hurricane Katrina two years ago. Although federal, state and local authorities were slow to react (and then even slower in the horrific aftermath), the advanced warnings and evacuations likely saved tens of thousands of lives. Had warnings been heeded earlier, perhaps many more could have been saved. It wasn't a lack of information that was the problem there...
So, astronomical science does have a beneficial impact for humans. The tax money spent on astronomy is relatively small (in 2006, a total of about 6 billion dollars, not including manned space flight. For comparison, this is 0.24% of the entire federal budget, or one quarter of a penny for every dollar you pay in federal taxes. It's also about 10% the size of the Department of Education budget or about 20% the size of the Housing and Urban Development budget for that year, and 1.5% the size of that year's Department of Defense funding, not including the costs of the ongoing wars in Iraq and Afghanistan). I'd like to think that the return on that investment is worthwhile, but, of course, I'm biased.